Interest in well-being has increased. This involves personal well-being as well as health care. This has resulted in many personal and medical monitoring devices, such as sensors. Such sensors can be embedded in clothing, such as gloves, mitts, footwear, helmets, etc. As for force or pressure sensors for garments, they may be e.g. piezo resistive, piezoelectric, or capacitive. A capacitive force/pressure sensor typically involves only easily available materials.
In capacitive sensors, the capacitance of an electrode is measured. The capacitance can be measured relative to surroundings or relative to another electrode, such a ground electrode. In general there are two working principles: (1) the dielectric material close to the electrode (e.g. in between two electrodes) changes, which changes the capacitance; and/or (2) the distance between two electrodes changes, which changes the capacitance in between these electrodes. These principles are known to a skilled person.
For example, the patent application DE102009055121 discloses a force sensor having multiple conductors and an elastic non-conductive layer in between. By applying force, the elastic non-conductive layer deforms, which results in a change of capacitance in between the conductors (i.e. electrodes).
In such sensors there are several interrelated problems. For example, the area of the electrodes should be reasonably large in order to measure the force accurately. Moreover, the measurement of the capacitance of an electrode should not affect the measurement result of the capacitance of another electrode. Furthermore, it would be beneficial that multiple capacitances can be measured in parallel, i.e. simultaneously or substantially simultaneously. For example, when monitoring the performance of a high jumper, one should be able to measure the pressure distribution under foot as function of time with reasonable high sampling rate. Moreover, the spatial resolution should be reasonably high, whereby the number of electrodes should be reasonably high. Still further, the sensor should be comfortable to wear and mechanically reliable.